Autoimmune diseases such as rheumatoid arthritis (RA) and multiple sclerosis (MS) are thought to result from breaks in tolerance. In the early stages, self-reactive T cells play a major role. Late stage progression is due primarily to the chronic inflammatory environment created by innate immune cells, i.e. macrophages and synoviocytes in RA and macrophages/microglia in MS. Effective therapies should address both early and late stages, avoid generalized immunosuppression, and have local rather than systemic effects. We showed previously that dendritic cells (DC) differentiated in the presence of the neuropeptide vasoactive intestinal peptide (VIP) become tolerogenic, and induce regulatory T cells (Treg). The VIP-induced DC (DCVIP) prevent collagen induced arthritis (CIA) and experimental autoimmune encephalomyelitis (EAE), stop disease progression in early stages, but do not affect innate immune cells responsible for later stages. Systemic VIP administration affects both T cells and suppresses the inflammatory activity of macrophages, synoviocytes, and microglia. However, the requirement for repeated, high VIP doses leads to side effects due to its pleiotropic functions. Therefore we propose to evaluate the therapeutic potential of genetically altered VIP expressing DC, which in addition to being tolerogenic, will deliver VIP locally, inhibiting the release of proinflammatory agents. The VIP-expressing DC (LentiVIP-DC) will be tested in EAE and CIA models. In Specific Aim 1, we propose to establish the best conditions for DC transduction. LentiVIP-DC will be analyzed in terms of phenotype, migration, cytokine profile and effects on T cells and macrophages. In Specific Aim 2 and 3 we propose to use LentiVIP-DC in EAE and CIA models. We will assess LentiVIP-DC migration to spleen, CNS, and affected joints, and investigate the effects on clinical disease, on splenic and local cytokine/chemokine expression and on T cell differentiation. The combined therapeutic approach using tolerogenic DC transduced with VIP-expressing lentiviral vectors should allow for the generation of antigen- specific Treg, as well as the local release of immunosuppressive VIP. This double-directional system represents a novel approach in the treatment of autoimmune diseases.